This invention relates generally to casings for watches, and more particularly to a waterproof casing for a solid-state electronic watch, the casing having two distinct sections, one for the electronic module and the other for batteries to power the module.
The term solid-state electronic timepiece, as used herein, is limited to timepieces provided with an electro-optic time display and having no moving parts. The traditional, springpowered mechanical watch produces rotary motion for driving gear works that operate the moving hands or time indicators. In those electronic watches which also have a moving hand read-out, the oscillations of a balance wheel or the vibrations of a tuning fork are electronically-sustained, those oscillations or vibrations being converted into rotary motion for driving the gear train. Hence moving parts are included in electronic timepieces of this type.
However, in recently-introduced types of solid-state electronic watches such as those disclosed in U.S. Pat. Nos. 3,756,103 and 3,759,031 electrical pulses derived from a crystal-controlled time base serve to actuate a multi-digit electro-optic display formed either by light-emitting diodes (LED) or by liquid-crystal elements (LCD). Hence in such solid-state electronic timepieces, no moving parts are entailed. In such solid state watches, the high-frequency output of the time base is fed to a frequency converter constituted by a chain of integrated circuit divider stages. The output of the converter consisting of low-frequency timing pulses (i.e. 1 Hz), is applied to a display actuator in the form of a miniature time-computer module that counts the input pulse train, encodes it in binary form and then decodes and processes the results so as to provide the appropriate signals at the display stations.
Battery-operated electronic watches, whether of the type having moving parts or of the solid-state type, require one or more miniature battery cells to power the electronic movement. Because these cells have a limited life and must be replaced from time to time, the design of the watch casing is necessarily such as to provide access to the cell. In some electronic watch designs, the back of the casing is removable by means of a special tool to expose both the electronic movement and the battery cell. Since a special tool is entailed and care must be exercised, the cell cannot safely be replaced by the watch owner but only by a qualified watch repairman. There are several practical drawbacks to this arrangement, for the owner cannot himself immediately replace a dead battery but must find and pay for the services of a repairman. Also because the entire movement is exposed when the casing back is removed, a careless replacement of the battery may result in damage to the movement.
In order to avoid having to remove the entire casing back in order to replace a battery cell, it is known to provide backs with threaded, disc-shaped waterproof hatches which may be removed by the owner by means of a coin to provide access only to the battery cell. This has the advantage of permitting the owner to replace the cell without having to engage a repairman, but this design involves a more costly casing.
Where, in the case of existing types of solid-state watches, it is necessary to provide two battery cells to produce a voltage whose level is sufficient to power the LCD or LED display, it is not feasible to have a casing with two access hatches, one for each battery, nor is it desirable to have a casing whose back must be removed in order to replace the cells, for in doing so the delicate electronic movement is exposed and may be damaged.
It must be borne in mind that in a solid-state watch, the electronic circuits are embodied in an integrated circuit chip which is connected by fine leads to a display unit, connections also being made to various control switches. Thus an electronic assembly or module can only be safely handled by a specialist, and should the casing arrangement be such as to expose the movement each time as battery change is made, the likelihood of damage to the movement is increased.